1. Field of the Invention
The invention relates to a coupling device of a vehicle seat. More specifically, the invention relates to a coupling device of a vehicle seat, which couples two subject members in a manner such that one of the two subject members is rotated relative to the other of the two subject members.
2. Description of the Related Art
Japanese Patent Application Publication No. 10-57175 (JP-A-10-57175) describes a vehicle seat in which a seat back is coupled to a seat cushion through a reclining device, and a tilt angle of the seat back is adjustable. In the publication, the reclining device is configured by combining a movable member with a fixed member in a manner such that the movable member and the fixed member are rotated relative to each other. The movable member is integrally coupled to a framework portion of the seat back. The fixed member is integrally coupled to a framework portion of the seat cushion.
A lock member is provided between the movable member and the fixed member. When the lock member is engaged with the movable member, the lock member locks the relative rotation of the movable member and the fixed member. More specifically, the lock member is guided in a manner such that the lock member is moved only in a radial direction of the fixed member. When external teeth formed in an outer peripheral surface of the lock member is engaged with internal teeth formed in an inner peripheral surface of the movable member, the relative rotation of the movable member and the fixed member is locked.
The above-described lock member is guided in a manner such that the lock member is moved only in the radial direction of the fixed member, by wall portions that are formed in the fixed member, and disposed on sides of the lock member. In the reclining device described in the publication No. 10-57175, when the lock member is engaged with the movable member to lock the lock member, the lock member is rotated so that portions of the lock member, which are located at diagonal positions, contact the respective wall portions, that is, the lock member is in point contact with the wall portions, to prevent the lock member from vibrating in a circumferential direction due to a gap between the lock member and each wall portion. Thus, although the lock member is easily placed with the certain gap between the lock member and each wall portion, it is possible to prevent the lock member from vibrating when the lock member is locked.
In the technology described in the publication, the lock member is supported in a manner such that the lock member is inclined with respect to the wall portions. Therefore, although a supporting force for supporting the lock member in one rotational direction is strong, a supporting force for supporting the lock member in the other rotational direction is weak.